Sheet feed mechanism



Sept. 15, 1964 R. H. EICHORN SHEET FEED MECHANISM 3 Sheets-Sheet 1 FiledApril 2, 1962 INVENTOR. RO GER H. E ICHORN ATTORNEY Sept. 15, 1964 H.EICH-OR 3,148,878

SHEET FEED MECHANISM Filed April 2, 1962 3 Sheets-Shee'f 2 ATTORNEY Set. 15, 1964 R. H. EICHQRN;

SHEET FEED 3 Sheets-Sweet 3 Filed April 2, 1962 INVENTOR ROGER H.ElCHORN ATTORNEY United States Patent 3,148,878 SHEET FEED MECHANISMRoger H. Eichorn, Webster, N.Y., assignor to Xerox Corporation,Rochester, N.Y., a corporation of New York Filed Apr. 2, 1962, Ser. No.184,205 6 Claims. (Cl. 271-79) This invention relates in general to asheet feed mechanism and, in particular, to a sheet conveyor mechanismfor seriatim feeding of sheet material to a xerographic drum.

Specifically, the invention relates to an improved sheet grippermechanism for a sheet conveyor that is particularly adapted for use in axerographic reproducing apparatus, and which is also suitable for usewith comparable types of devices.

In the process of xerography, for example, as disclosed in eitherCarlson Patent 2,297,691, issued October 6, 1942, or in Carlson Patent2,357,809, issued September 12, 1944, a xerographic plate, comprising alayer of photoconductive insulating material on a conductive backing, isgiven a uniform electrostatic charge over its surface and is thenexposed to the subject matter to be reproduced, usually by conventionalprojection techniques. This exposure discharges the plate areas inaccordance with the radiation intensity which reaches them and therebycreates an electrostatic latent image on or in the plate coating.

Development of the image is effected with developer material ordevelopers which comprise, in general, a mixture of a suitable pigmentedor dyed electroscopic powder, hereinafter referred to as toner, and agranular carrier material, which latter functions to carry and togenerate triboelectric charges on the toner. More exactly, the functionof the granular material is to provide the mechanical control to thepowder, or to carry the powder to an image surface and, simultaneously,to provide almost complete homogeneity of charge polarity. In thedevelopment of the image, the toner powder is brought into surfacecontact with the xerographic plate and is held thereon electrostaticallyin a pat-tern corresponding to the electrostatic latent image.Thereafter, the Xerographic powder image is transferred to a supportmaterial to which it may be fixed by any suitable means.

The invention relates to conveyors and in particular to sheet grippermechanisms for conveying sheet material, such as paper or the like, tocontact the xerographic plate in synchronized movement therewith wherebythe developed xerographic image from the xerographic plate istransferred in proper registration onto the sheet material.

Because of cost and other considerations, it is desirable to use in thesheet conveyor, roller chains having relatively small diameter rollers.It is also desirable to have the sheet grippers carried by the rollerchains of a minimum thickness, preferably of a thickness correpsondingto the thickness of the roller chains.

It is apparent that the sheet gripper elements cooperating with eachother to grip a sheet must be biased into cooperative engagement tosecurely grip the sheet. Because this biasing force can be relativelylarge whereas the thickness of the sheet gripper is relatively small, asheet gripper of suflicient length to grip wide sheet material canreadily be twisted or deflected as the sheet gripper is caused by camaction to open to receive, or reject sheet material.

It is therefore the principal object of this invention to improve sheetfeeding mechanisms for use in a xerographic apparatus or similar device.

A further object of this invention is to improve sheet gripper devicesand their actuators to sheet gripper devices to securely grip wide sheetmaterial without deflection of the sheet gripper devices.

3,l48,8?8 Patented Sept. 15., 1964 "ice Another object of this inventionis to improve sheet gripper devices for use in a sheet conveyor wherebyvarious sized sheet material can be conveyed.

These and other objects of the invention are attained by means of asheet conveyor including two endless belts, in the form of rollerchains, supported by pulley means for travel in unison in twospacedsubstantially parallel planes to transport a sheet gripper mechanismfrom a sheet receiving station to a sheet delivery station. The sheetgripper mechanism includes a gripper bar connected to the endless beltsalong a line perpendicular to the spaced planes of travel of the endlessbelts. The gripper bar supports sheet gripping means including at leastone movable gripper having a jaw adapted to cooperate with the jaw of asecond gripper to grip a sheet therebetween. Pairs of cam means arelocated adjacent and between the endless belts at the sheet receivingstation and the sheet delivery station. The cam means include a firstcam and a second cam mounted in spaced relation to each other forpassage of the sheet gripper mechanism between the cams whereby thesheet gripper mechanism is supported and actuated by these cams.

For a better understanding of the invention as well as other objects andfurther features thereof, reference is had to the following detaileddescription of the invention to be read in connection with theaccompanying drawings, wherein:

FIG. 1 is a schematic illustration of a xerographic reproducingapparatus having a'sheet feed mechanism using a preferred embodiment ofa sheet gripper mechanism of the invention;

FIG. 2 is an enlarged side view of the sheet gripper mechanism and camarrangement of FIG. 1;

FIG. 3 is a front view of the sheet gripper mechanism of FIG. 2;

FIG. 4 is an enlarged perspective view of the sheet gripper mechanism ofFIG. 2;

FIG. 5 is an enlarged side view of a second embodiment of a sheetgripper mechanism;

FIG. 6 is an enlarged perspective view of the sheet gripper mechanism ofFIG. 5; and

FIGS. 7, 8 and 9 are side views illustrating schematically the sequenceof operation of the sheet gripper mechanism of FIG. 5 and the camarrangement for effecting its operation.

General As shown, the xerographic apparatus comprises a xerographicplate including a photoconductive layer or lightreceiving surface on aconductive backing and formed in the shape of a drum, generallydesignated by numeral 16, which is journaled in a frame to rotate in thedirection indicated by the arrow to cause the drum surface sequentiallyto pass a plurality of Xerographic processing stations.

For the purpose of the present disclosure, the several Xerographic'processing stations in the path ofmovement of the drum surf-ace may bedescribed functionally, as follows:

A charging station, at which a uniform electrostatic charge is depositedon the photoconductive layer of the xerographic drum;

' to form a xerographic powder image in the configuration on the copy tobe reproduced;

A transfer station, at which the xerographic powder image iselectrostatically transferred from the drum surface to a transfermaterial or support surface; and

A drum cleaning and discharge station, at which the drum surface isfirst charged and then brushed to remove residual toner particlesremaining thereon after image transfer, and at which the drum surface isexposed to a relatively bright light source to effect substantiallycomplete discharge of any residual electrostatic charge remainingthereon.

The charging station is preferably located as indicated by referencecharacter A in the schematic illustration of the apparatus. In general,the charging apparatus or corona charging device 11; includes a coronadischarge array of one or more discharge electrodes that extendtransversely across the drum surface and are energized from a highpotential source and are substantially enclosed within a shieldingmember.

Next subsequent thereto in the path of motion of the xerographic drum isan exposure station B. This exposure station may be one of a number oftypes of mecha nisms or members such as desirably an optical scanning orprojection system or the like designed to project a line copy image ontothe surface of the photoconductive xerographic drum from a suitableoriginal.

The optical scanning or projection assembly consists of a copyboard inthe shape of a drum, hereinafter referred to as copy drum 12, which isadapted to support copy to be reproduced and arranged to rotate inlight-projection relation to the moving light-receiving surface of thexerographic plate. Uniform lighting is provided by suitable lampsattached to a slotted light reflector 13 mounted adjacent to the copydrum.

A light shield 14 adapted to protect the xerographic plate fromextraneous light is positioned adjacent to the surface of thexerographic plate. A slot aperture 15 in the light shield extendstransversely to the path of movement of the light-receiving surface ofthe xerographic drum It) to permit reflected rays from the copy drum tobe directed against a limited transverse area of the light-receivingsurface as it passes therebeneath.

To enable the optical system to be enclosed within a relatively smallcabinet, a folded optical system including van object mirror 16, a lens1?, and an image mirror 18 is used in the preferred embodiment of theapparatus.

Copy fed through paper guides 21 to the copy drum is removably securedthereon by a suitable gripper mechanism for movement therewith in timedrelation to the movement of the xerographic drum whereby a flowing imageof the copy is projected onto the xerographic drum. The copy is heldagainst the surface of the copy drum by means of guides 22 and 23, thelatter also preventing the trailing edge of the copy from contacting theweb cleaner. After the copy is scanned, it can be released from the copydrum to be transported out of the machine by copy feed out roller 24coacting with the peripheral surface of the copy drum to forward thecopy through copy guide 25.

Adjacent to the exposure station is a developing station C in whichthere is positioned a developer apparatus 26 including a developerhousing having a lower or sump portion for accumulating developermaterial 27. Mounted within the developer housing is a motor drivenbuckettype conveyor used to carry the developer material previouslysuppied to the developer housing to the upper portion of the developerhousing from where the developer material is cascaded over a hopperchute onto the drum.

As the developer material cascades over the drum,

7 toner particles of the developer material adhere electrostatically tothe previously formed electrostatic latent image areas on the drum toform a visible xerographic powder image; the remaining developermaterial falling off the peripheral surface of the drum into the bottomof the developer housing. Toner particles consumed during the developingoperation to form the xerographic powder images are replenished by asuitable toner dispenser 23 mounted within the developer housing.

Positioned next adjacent to the developing station is the image transferstation D which includes suitable sheet feeding mechanism adapted tofeed'sheets of paper successively to the xerographic drum incoordination with the presentation of the developed image on the drumatthe transfer station. The sheet feeding mechanism includes a sheetsource such as tray 31 for a plurality of sheets of a suitable material,that is, sheets of paper or the like. A separator roller 32 ispositioned to feed the top sheet of the stack of material through apaper guide 33, provided with a suitable gate at one end, to a sheetconveyor mechanism 34 constructed in accordance with the invention. Thesheet conveyor mechanism is provided with one or more sheet grippermechanisms 35, constructed in accordance with a preferred embodiment ofthe invention, which carry the sheet support matermial into contact withthe rotating xerographic drum in coordination with the appearance of adeveloped image at the transfer station. Suitable means, such as cams 36connected to the chains of the conveyor mechanism, are provided to openthe gate of the paper guide to release a sheet to the sheet grippermechanism as it is opened at the sheet receiving station.

The transfer of the xerographic powder image fromthe drum surface to thesupport material is effected by means of a corona transfer device 41that is located at or immediately after the point of contact between thesupport material and the rotating xerographic drum. The corona transferdevice 41 is substantially similar to the corona taneously with thetacking action, the electrostatic field is effective to attract thetoner particles comprising the xerographic powder image from the drumsurface and cause them to adhere electrostatically to the surface of thesupport material.

As the paper gripper mechanism continues to move forward in its closedcircuit, it will strip thesupport ,material from the xerographic drumand carry it to a fixing device, such as, for example, heat fuser 42,whereat the developed and transferred xerographic powder image on thesupport material is permanently fixed thereto.

After fusing, the finished copy is preferably discharged from theapparatus at a suitable point for collection externally of theapparatus. To accomplish this, there i provided a pair of delivery rolls43 and 44 by means of which the copy is delivered to a copy holder afterit is released by the gripper mechanism. Cam elements, described indetail hereinafter, are provided at the receiving and delivery stationsof the conveyor mechanism to actu- .ate the sheet gripper mechanism atthese stations to receive or discharge a sheet of support material.

The next and final. station in the device is a drum cleaning station Ewhereat any powder remaining on to and around a set of sprockets 64 onshaft 65.

xerographic drum is effected by means of web cleaner device 52 adaptedto continuously feed a clean fibrous web material into wiping contactwith the xerographic drum. As shown, the web material 53 is taken from asupply roll 54 and transported around a cleaning roll 55, preferablymade of rubber, around a guide plate 56 to be wound onto take-up roll57.

Any residual electrical charge remaining on the xerographic drum isdissipated by light from a fluorescent lamp 58 mounted in a suitablebracket above the xerographic drum, a suitable starter and ballast beingprovided for energizing the fluorescent lamp.

Suitable drive means drive the xerographic drum, the copy drum, thesheet conveyor mechanism at predetermined speeds relative to each other,and effect operation of the paper separator roll, and the web cleanermechanism, the latter being driven at a speed or speeds whereby relativemovement between the xerog-raphic drum and the web material is effected.Suitable drive means are also provided for effecting operation of theconveyor mechanism and toner dispenser of the developing apparatusassembly.

Referring now to the subject matter of the invention, the sheet conveyormechanism 34 includes two endless belts, in the form of roller chains61, which extend from a set of drive sprockets 62 carried by shaft 63These two sets of sprockets are fixedly positioned on their respectiveshafts to space the roller chains apart from each other by a distancegreater than the length of the drum to afford complete use of thexerographic drum Surface.

In the embodiment of the sheet conveyor mechanism shown, the rollerchains carry two sheet gripper mechanisms. The sheet gripper mechanisms35 are equally spaced from each other along the length of the chains,and positioned on the chains at right angles to the path of travel ofthe chains for movement therewith in a circuit between sheet receivingand sheet delivery stations, identified as the output area of the paperguide 33, and the delivery rollers 43 and 44, respectively. Cam elementsare provided at these stations to actuate the sheet gripper mechanisms.

Two paper grippers are used in the machine shown so that as one sheetgripper mechanism is moved from the receiving station carrying sheetmaterial to the delivery station, the other sheet gripper mechanism willadvance from the delivery station to the receiving station to be inposition to receive the next sheet from paper guide 33.

Referring now to the subject matter of the invention, there is shown inFIGS. 1, 2, 3 and 4, a preferred embodiment of a sheet gripper mechanismadapted to accommodate various sized sheets.

As shown, each sheet gripper mechanism 35 includes a gripper bar bracket71 of a length to extend substan tially between the two roller chains 61to be connected thereto by means of clips 74 forming part of the chainswhen connected thereto, as is well known in the art. A support bar 72,which may be formed as a separate element fixed to the gripper barbracket, as shown, or formed integral therewith extends across thegripper bar bracket to form a more rigid member.

Individual jaws are formed by a plurality of sets of sheet grippers 81and 85. The sets of sheet grippers 81 and 85 are mounted by means ofpins 75 secured to the curved pin support portions of the gripper barbracket.

Sheet grippers 81, although shown as separate elements secured by pins75 to the gripper bar bracket, may be formed integral with the gripperbar bracket. As shown, each sheet gripper 81 is provided with spaced legportions 82 which serve as a guide and stop to align the leading edge ofa sheet inserted into the sheet gripper mechanism, and with a jawportion 83 which cooperates with the tang portion or jaw 86 of therespective sheet gripper with which it is aligned on the gripper barbracket.

Each sheet gripper 85 is mounted by a pin 75 for movement in twodirections relative to its cooperating fixed sheet gripper 81; that is,for movement from a first position in which its tang portion or jaw 86is in spaced relation to the jaw portion 83 of sheet gripper 81, to asecond position in which the tang portion or jaw 86 is in engagementwith the jaw portion 83 of sheet gripper 81, or with a sheet sandwichedtherebetween.

Each sheet gripper 85 is provided with a work arm or cam portion 87 atits front end (in terms of the direction of travel of the gripper barbracket) which serves as a lever by means of which the sheet gripper isactuated.

The tang portion or jaw 86 of a sheet gripper 85 is normally biased intocooperative gripping relation with the jaw portion 83 of a sheet gripper81, by means of spring 76. In order to resiliently hold the tang or jawof sheet gripper 85 in gripping relation to the jaw portion 83, spring76 is mounted with its coiled portions encircling pin 75. The centralportion of the spring engages the work arm or cam portion 87 of sheetgripper 85 and the arm portions of the spring engage the sheet gripper81.

In a xerographic reproducing apparatus used to make reproductions onwide sheets of paper, it is apparent that the sheet gripper mechanismmust be of a length greater than the width of the largest sheet on whicha reproduction is to be made.

In handling large sheets, it is necessary to securely grip the leadingedge of a sheet without deflection of the sheet gripping mechanism as itis actuated by an operating mechanism to receive or release a sheet.

In the arrangements of the operating mechanism shown, the sheet grippermechanism, provided with a plurality of sets of sheet grippers, isactuated in a manner whereby the load imposed by the individual sets ofsheet grippers as they are actuated is transposed equally to two supportmembers.

In the preferred embodiment of an operating mechanism, as shown at thereceiving station in FIG. 1, and in FIGS. 2 and 3, the operatingmechanism consists of two rollers 91 and 93, mounted on shafts 92 and94, respectively, spaced on opposite sides of the path of travel of thesheet gripper mechanisms.

Although individual sets of rolls 91 and 93 are shown for each set ofsheet grippers, it is apparent that a single set of rolls extendingacross the full length of the sheet gripper mechanism can be used.

Although the rolls 91 and 93 may be journaled on their respective shaftsfor rotation relative thereto, the rolls are preferably fixed to theirrespective shafts and the shafts are driven at a speed whereby thelinear speed of the roll is equal to and in the same direction as thespeed of movement of the sheet gripper mechanism to eflfect rollingcontact between the rolls and the sheet grippers. This reduces thefrictional contact between these elements and reduces the forces actingon the chains during opening of the sheet gripper mechanism.

In operation, the sheet gripper mechanism is carried between the gapimposed by the rolls. The action of the work arm of each sheet gripper85 as it contacts a roll 93 opens the sheet gripper against the biasingaction of the springs 76. Heavy springs, in terms of theirbiasing force,can be used since the sheet gripper mechanism is supported on oppositesides and the resultant force, as the sheet grippers are opened, isreduced to substantially zero as far as deflection of the gripper barbracket is concerned.

Another embodiment of an operating mechanism to actuate the sheetgripper mechanism is shown at the delivery station of the xerographicreproducing apparatus, in FIG. 1. In this embodiment, a rotatable roll91, mounted on shaft 92, and a stationary cam 95 are used to actuate andto prevent deflection of the sheet gripper mechanrsm.

In the embodiment shown in FIGS. through 9, inclusive, the sheet grippermechanism includes a gripper bar bracket 101 and support bar 102 similarin construction to the gripper bar bracket 71 and support bar 72,respectively. A plurality of sets of sheet grippers 111 and 115, formedcomplementary to each other, are pivotally connected to the gripper barbracket by pins 75, for movement with respect to the gripper bar bracketand with respect to each other.

Sheet gripper 111, is provided with a jaw 112 adapted to cooperate withthe tang portion or jaw portion 116 of sheet gripper 115. Sheet gripper111 is also provided with a work arm or cam portion 113 at its front end(in terms of the direction of travel of the sheet gripper mechanism).

Sheet gripper 115, similar in construction to sheet gripper 85, is alsoprovided with a work arm or cam portion 117.

In order to resiliently hold the jaw 112 of sheet gripper 111 ingripping relation to the tang portion or jaw 116 of sheet gripper 115, aspring 118, similar to spring 76, encircles an intermediate portion ofpin 75 with one end portion of the spring engaging the cam followerportion 113 of the sheet gripper 111 and the opposite end portion of thespring engaging the work arm or cam portion 117 of sheet gripper 115.

As shown in FIG. 6, the work arm 113 of sheet gripper 111 is preferablyformed with a reduced central portion adapted to clear the bifurcatedwork arm 117 of sheet gripper 115 whereby these work arms willintercross as they are actuated.

It is apparent that a sheet conveyor mechanism having a sheet grippermechanism of the type disclosed can be constructed to accommodate largesize sheets while still permitting the conveyor to operate effectivelyon smaller size sheets.

For example, when it is desired to convey two or three foot width paper,six or eight sets of sheet grippers can be positioned across the lengthof the gripper bar bracket, with each set being biased into grippingengagement by a relatively heavy torsion spring. However, the resultantforce, as the sets of sheet grippers are actuated, is reduced tosubstantially zero as far as deflection of the gripper bar bracket isconcerned.

Sheets of paper of any size are held uniformly along substantially theentire leading edge of the sheets because of the novel arrangement ofthe sheet gripper mechanisms and their operating mechanisms.

While the invention has been described with reference to the structuresdisclosed herein, it is not confined to the details set forth, and thisapplication is intended to cover such modifications or changes as maycome within the purposes of the improvements or the scope of thefollowing claims.

What is claimed is:

1. A sheet conveyor including two endless belts,

pulley means supporting said endless belts for travel in unison in twospaced planes,

a gripper bar bracket connected at opposite ends to said endless beltsalong a line substantially perpendicular to the two spaced planes oftravel of said endless belts,

a plurality of first sheet grippers and an equal number of second sheetgrippers mounted on said gripper bar bracket,

said first sheet grippers and said second sheet grippers each having jawportions adapted to cooperate with each other to grip a sheettherebetween,

at least said first sheet grippers being pivotally mounted on saidgripper bar bracket and each having a cam follower portion thereon,

spring means connected to each set of said first sheet gripper and tosaid second sheet gripper pairs to normally bias said jaw portions ofsaid sheet grippers into cooperative engagement with each other,

and operating means positioned adjacent said belts and on opposite sidesof the path of travel of said gripper bar bracket adapted to contactsaid grippers to actuate said sheet grippers on opposite sides of saidgripper bar bracket and to support said sheet grippers to preventdeflection of said gripper bar bracket.

2. The apparatus of claim 1,

wherein said operating means includes first roller means positioned forrolling contact with said first sheet gr1ppers and a second roller meanspositioned for rolling contact with said second sheet grippers.

3. The apparatus of claim 2,

wherein said second sheet grippers are pivotally mounted on said gripperbar bracket and each of said second sheet grippers are provided with acam follower portion adapted to actuate said second sheet grippers whensaid cam follower portion of each of said second sheet grippers contactssaid second roller means.

4. A sheet conveyor including two endless belts,

pulley means supporting said endless belts for travel in unison in twospaced planes,

a gripper bar bracket connected at opposite ends to said endless beltsalong a line substantially perpendicular to the two spaced planes oftravel of said endless belts,

a plurality of first sheet grippers and an equal number of second sheetgrippers; and an equal number of pins secured on said gripper barbracket,

said first sheet grippers and said second sheet grippers beingpositioned on opposite sides of said gripper bar bracket and pivotablymounted in sets in cooperative relation to each other by said pins,

said first sheet grippers and said second sheet grippers each having jawportions adapted to cooperate with each other to grip a sheettherebetween,

at least each of said first sheet grippers having a cam follower portionthereon,

spring means connected to each set of said first sheet gripper and tosaid second sheet gripper sets to normally bias said jaw portions ofsaid sheet grippers into cooperative engagement with each other,

and operating means positioned adjacent said belts and on opposite sidesof the path of travel of said gripper bar bracket in position to contactsaid sheet grippers to actuate said sheet grippers and to support saidsheet grippers to prevent deflection of said gripper bar bracket as saidsheet grippers are actuated.

5. The apparatus of claim 4,

wherein said operating means includes a first roller means positionedfor rolling contact with said first sheet gripper and a second rollermeans positioned for rolling contact with said second sheet gripper.

6. The apparatus of claim 5,

wherein said second sheet grippers are each provided with a cam followerportion adapted to actuate said second sheet grippers when said camfollower portion of each 'of said second sheet grippers contacts saidsecond roller means.

References Cited in the file of this patent UNITED STATES PATENTS716,576 Pancoast Dec. 23, 1902 1,543,374 Everett June 23, 1925 1,613,445Davis et al Jan. 4, 1927 2,173,952 Ranney Sept. 26, 1939 2,418,065 BobstMar. 25, 1947 2,950,914 Golding Aug. 30, 1960

1. A SHEET CONVEYOR INCLUDING TWO ENDLESS BELTS, PULLEY MEANS SUPPORTINGSAID ENDLESS BELTS FOR TRAVEL IN UNISON IN TWO SPACED PLANES, A GRIPPERBAR BRACKET CONNECTED AT OPPOSITE ENDS TO SAID ENDLESS BELTS ALONG ALINE SUBSTANTIALLY PERPENDICULAR TO THE TWO SPACED PLANES OF TRAVEL OFSAID ENDLESS BELTS, A PLURALITY OF FIRST SHEET GRIPPERS AND AN EQUALNUMBER OF SECOND SHEET GRIPPERS MOUNTED ON SAID GRIPPER BAR BRACKET,SAID FIRST SHEET GRIPPERS AND SAID SECOND SHEET GRIPPERS EACH HAVING JAWPORTIONS ADAPTED TO COOPERATE WITH EACH OTHER TO GRIP A SHEETTHEREBETWEEN, AT LEAST SAID FIRST SHEET GRIPPERS BEING PIVOTALLY MOUNTEDON SAID GRIPPER BAR BRACKET AND EACH HAVING A CAM FOLLOWER PORTIONTHEREON, SPRING MEANS CONNECTED TO EACH SET OF SAID FIRST SHEET GRIPPERAND TO SAID SECOND SHEET GRIPPER PAIR TO NORMALLY BIAS SAID JAW PORTIONSOF SAID SHEET GRIPPERS INTO COOPERATIVE ENGAGEMENT WITH EACH OTHER, ANDOPERATING MEANS POSITIONED ADJACENT SAID BELTS AND ON OPPOSITE SIDES OFTHE PATH OF TRAVEL OF SAID GRIPPER BAR BRACKET ADAPTED TO CONTACT SAIDGRIPPERS TO ACTUATE SAID SHEET GRIPPERS ON OPPOSITE SIDES OF SAIDGRIPPER BAR BRACKET AND TO SUPPORT SAID SHEET GRIPPERS TO PREVENTDEFLECTION OF SAID GRIPPER BAR BRACKET.